A high-temperature gas-cooled reactor which is one type of a nuclear reactor employs, as fuels, coated-particle fuels that are nuclear fuels being clad with heat-resistant pyrolytic carbons (PyC) and silicon carbides (SiC) and also employs heat-resistant graphite for the retarder and the in-core structural materials, wherein helium gas is used for the coolant thereof. In addition, block type of fuels being graphite blocks with fuel rods inserted therein and pebble bed fuels being spherically compact are employed as coated-particle fuels to be used for a high-temperature gas-cooled reactor. Then, by having the reactor core composed of ceramics instead of metal materials, the reactor core can withstand very high temperature nearly as high as 1000° C.
In consequence, by utilizing the heat generated by a high-temperature gas-cooled reactor, high outlet gas temperature of over 800° C. that cannot be achieved by other types of nuclear reactor can be attained, thereby achieving electrical power generation of high thermal efficiency. In addition, the fuels to be used are superior in safety because fuel melting and breakage of a coating layer scarcely occur when the fuel temperature increases, and fission products are maintained even in accident conditions. Moreover, in Japan, a “High Temperature Engineering Test Reactor” (HTTR) is operated as a high-temperature gas-cooled reactor.
In an electrical power generation plant, such a high-temperature gas-cooled reactor as described hereinabove is employed for the steam cycle electric power generation in which steam is generated by high temperature gas from a high-temperature gas-cooled reactor, so as to drive a steam turbine, and is employed for the closed cycle gas turbine electric power generation in which a gas turbine is driven by high temperature gas from a high-temperature gas-cooled reactor. Here, in a steam turbine electrical power generation having steam conditions being equivalent to those of conventional thermal electrical power generation, approximately 40% thermal efficiency is achieved, but by employing the closed cycle gas turbine electrical power generation having the nuclear reactor coolant outlet temperature of approximately higher than 850° C., there is a possibility of achieving the thermal efficiency ranging from 45% to 50%.
Then, as a high-temperature gas-cooled reactor utilized in the closed cycle gas turbine electrical power generation having high thermal efficiency, is disclosed a high-temperature gas-cooled reactor in a gas turbine plant in which a system circulating in the high-temperature gas-cooled reactor is different from a system circulating in the gas turbine. (See the Patent Literature 1.) In the gas turbine plant being disclosed in the Patent Literature 1, helium gas in the secondary circuit is heated by high temperature helium gas being obtained by the high-temperature gas-cooled reactor provided to the primary circuit, and then, a gas turbine is driven by the heated helium gas in the secondary circuit.
Additionally, the present applicant disclosed a gas turbine plant in which a gas turbine sharing a same shaft with a high pressure compressor and a gas turbine sharing a same shaft with a generator are provided in such a manner as to be connected by different shafts and the gas turbines being connected by the different shafts are driven by helium gas from a high-temperature gas-cooled reactor. (See the Patent Literature 2.) In this gas turbine plant, helium gas discharged from the gas turbines is supplied to the high-temperature gas-cooled reactor after being compressed by a compressor. A “Pebble Bed Modular Reactor” (PBMR) has been developed, which is employed for such a gas turbine plant as described hereinabove and is provided with a pebble bed reactor core using pebble bed fuels.
Moreover, the gas turbine plant in the Patent Literature 2 is a gas turbine plant that is provided with two-shaft gas turbines, wherein a gas turbine connected to a generator by a same shaft is also connected to a low pressure compressor by the same shaft. As a result, is increased a load which is to be applied to a gas turbine being connected to a low pressure compressor and a generator by one shaft. Therefore, a gas turbine plant using the “PBMR” has been developed, wherein, in order to distribute the load, a gas turbine being connected to a low pressure compressor by one shaft is provided and a gas turbine plant including three-shaft gas turbines is adopted.
Patent Literature 1: Patent Application Laid Open as H08-338892.
Patent Literature 2: Patent Application Laid Open as H9-144557.